1. Field of the Invention
The present invention relates to a mixer circuit, and particularly to a single-balanced mixer.
2. Description of the Related Art
In wired or wireless communication, a mixer circuit is used for up-conversion where a carrier is modulated by using a modulating signal and for down-conversion where the frequency of a modulated carrier is converted into a low-frequency band. A Gilbert-cell type single-balanced mixer is widely used as a mixer circuit.
A Gilbert-cell mixer is provided with a constant electric current circuit, a transistor to which a first signal is input, a transistor to which a second signal is input, and an impedance circuit, all stacked between a ground terminal and a power supply voltage terminal.
[Patent document 1] Japanese Patent Application (Laid-Open) No. 2003-318674
In recent years, with the miniaturization of the semiconductor process, reduction of operating voltage for a circuit is progressing. In this instance, the use of a conventional Gilbert-cell mixer creates the problem of producing a distorted output signal due to the saturation of transistors that are stacked in multi-levels.